In recent years, various health check chips have been developed. Most of these health check chips are a card device called “μ-TAS” (Micro Total Analysis System), which has a miniature flow path structure. A miniaturized flow path is very useful in that the required amount of a sample to extract from a living organism is small. Further, by making small entire apparatuses including the health check chip by miniaturizing the flow path, the apparatuses are applicable for use in POCT (Point of Care Test) that allows diagnosis in doctor's offices and households, not only in relatively large-scale hospitals.
In cases where a large amount of fluid flows, a pump is generally used as a liquid transferring means. However, in a miniature flow path that allows only a very small amount of fluid flows, it is not possible to pass over the dead volume in tube connected with the pump. Therefore, a pump is often not suitable for the liquid transfer means of a chip used in POCT.
Using centrifugal force for the source drive is suitable for a method liquid transfer in POCT (for example, Patent Documents 1 to 4). A method of liquid transfer by centrifugal force offers an advantage of not generating a dead volume and performing many processes at the same time in parallel.
For example, the substrate disclosed in Non-Patent Document 1 has a plurality of micro-chambers and micro-flow paths. In the substrate, the width of the micro-flow path connecting between the micro-chambers is adjusted. To be more specific, in a range between about 10 and 100 μm, micro-flow path that are more distant from the center of rotation has a narrower width. By this means, micro-flow path that is more distant from the axis of rotation generate greater capillary force. Liquid in a miniature chamber in which liquid transfer is blocked by the capillary force generated in the micro-flow path, is transferred to the neighboring micro-chamber in the centrifugal direction by the centrifugal force generated by the rotation of the substrate. The centrifugal force required to transfer liquid in a micro-chamber corresponds to the capillary force generated in the micro-flow paths. As described above, the micro-flow path is designed to generate greater capillary force as distant from the axis of rotation. Therefore, without increasing the speed of rotation, it is not possible to transfer liquid from one micro-chamber to neighboring micro-chamber in the centrifugal direction. That results in realizing stepwise liquid transfer.    Patent Document 1: Japanese Patent Application Laid-Open No. 2000-065778    Patent Document 2: Japanese Translation of a PCT Application Laid-Open No. 2001-503854    Patent Document 3: Japanese Translation of a PCT Application Laid-Open No. 2002-503331    Patent Document 4: Japanese Translation of a PCT Application Laid-Open No. 2000-514928    Non-Patent Document 1: Micro Total Analysis Systems 2000, pp. 311-314